SketchWave Ellipse Demo

SWEllipse is defined by a center SWPoint, a horizontal radius (radiusX), and a vertical radius (radiusY). Rotation is applied using p5's push()/translate()/rotate()/pop() pattern, so it is always smooth regardless of the shape's proportions.

Key Properties

• area — π × radiusX × radiusY
• perimeter — Ramanujan's approximation formula
• eccentricity — e = √(1 − (b/a)²); 0 for a circle, approaches 1 for very elongated shapes
• focalDistance — distance from center to each focus: c = √(a² − b²)
• semiMajorAxis, semiMinorAxis — the longer and shorter radii
• isCircle — true when radiusX ≈ radiusY (within 1% tolerance)

Foci (F)

Every ellipse has two focal points lying on the major axis. They are shown as orange dots. The foci rotate correctly with the ellipse. When isCircle is true, the foci coincide at the center and are not drawn.

Breathing Modes

• Uniform — both radiusX and radiusY pulse with the same sinusoid
• Horizontal — only radiusX breathes; radiusY stays constant
• Vertical — only radiusY breathes; radiusX stays constant
• Independent X/Y — separate sinusoids for each axis, enabling complex pulsing patterns

How to Use This Demo

• Radius X / Y Sliders: Independently control horizontal and vertical radii.
• Foci Toggle (F): Show or hide the two focal points as orange dots.
• Breathing: Click "Start Breathing" or press B.
• Spinning: Click "Start Spinning" or press S. Negative rate = CCW.
• Drag Center: When animations are paused, drag the ellipse center to reposition it.
• Trail (Center): Increase the trail slider to draw a path behind the center point.
• Keyboard: B breathe, S spin, F foci, C center, G grid, R reset, Q quit.

Learn More

For complete SWEllipse API documentation, visit the SWEllipse Reference.